Unsafe use of MOI

[mlubin]

The code below is accessing fields in a way that assumes jm_cache is a MOI.Utilities.UniversalFallback. This doesn't match the type of the argument (MOI.ModelLike) and could break in multiple ways. You should use the MOI API instead to query properties like variable bounds and starts.

https://github.com/exanauts/ExaModels.jl/blob/0ac40c25602229ecf8c65f5cf1ae70a13f1348bd/ext/ExaModelsMOI.jl#L58C10-L78

CC @blegat